The invention relates to a rotor with integrated blading, particularly for a propulsion plant. Rotor blades are arranged circumferentially around and extend essentially radially from the rotor.
Conventional fan rotor blades of fiber-reinforced synthetic material have a relatively large diameter, for example 3.2 m. Such fan rotor blades are produced as a solid construction with an integrated dovetail root or as a hollow construction with an internal piece, a so-called spar. The use of fiber-reinforced synthetic material, so-called composite material for blade sections, instead of metal, has the advantage of a substantial weight reduction. The described construction, however, is not suitable for smaller fan rotor blades operating at higher circumferential speeds because they cannot withstand the prescribed load caused by a bird impact. In order to nevertheless make use of the weight advantage, a blade section of fiber-reinforced synthetic material is attached at the blade root in a metallic retaining yoke. This hybrid construction has the disadvantage that the blade sections of synthetic material lack ductility. As a result, too large parts of the blade sections can break off upon a bird impact so that the propulsion plant can no longer provide the necessary emergency power. Furthermore, the retaining yoke is open toward the leading edge and the trailing edge of the blade and is torsionally soft. Moreover, the blade section of composite material is not protected against erosion.
German Patent Publication DE-OS 20 42 665 discloses a compressor blade that comprises a metal component that forms the entering or leading edge profile portion of the blade and a fiber-containing composite component that forms the remaining portion of the airfoil profile. The composite component of the airfoil is received in a groove in the metal component, and the metal component has a shaft for detachably connecting the compressor blade to a rotor disk.
German Patent Publication DE 195 35 713 A1 discloses a composite blade on which sections of the trailing edge are covered with a metallic cladding to reduce material losses on the trailing edge.
German Patent Publication DE 26 31 856 C2 discloses a compressor blade of a composite material, in which the fiber material is partially protected, at least on the leading side, with a metallic edge protector. The compressor blade has a dovetail for detachable attachment to a rotor.
U.S. Pat. No. 3,883,267 discloses a blade for a gas turbine with a metallic core having in a curved shape, around which a blade pan section of fiber-reinforced material is constructed.
The rotor blades are generally detachably secured to the circumferential surface of a rotor carrier, for example with a dovetail connection. The vibrations that occur during operation are thereby attenuated by the friction between the dovetail at the blade root and the corresponding groove in the rotor carrier. Such attenuation is lacking on integrally bladed rotors. As a result, the vibrations that occur during operation and the fatigue notching effect resulting from defective points occurring on the blade section, such as cracks, present a problem.
An object of the invention is to provide a rotor with integrated blading of the type described above, that will reduce the vibrations occurring during operation. In addition, the blading should also be as lightweight as possible.
The foregoing objects have been achieved according to the invention in that the present rotor blades have a metallic blade root, a metallic blade first blade section that forms at least a portion of the blade leading edge and the surface area adjacent to the leading blade edge, and a second blade section made of fiber-reinforced synthetic or composite material. More specifically, a compressor rotor according to the invention comprises said compressor rotor comprising a rotor blade carrier, rotor blades secured to said rotor carrier, each rotor blade comprising a metal blade root securing said rotor blade to said rotor carrier, a first blade section made of metal and a second blade section made of fiber composite material, said first metal blade section forming at least a portion of a blade leading edge, said second fiber composite material blade section forming a blade trailing edge, means connecting said first metal blade section and said second fiber composite material blade section to each other along a trailing rim of said first metal blade section, and wherein said first metal blade section has a radial length along said leading edge shorter than a length of said leading edge and a surface area extending between said radial length and said trailing rim so that said surface area has a size enabling said propulsion plant to deliver emergency power even if said second fiber composite material blade section is broken off.
The advantage results from the fact that such rotor blades, on the one hand, provide significant weight advantages over metallic blades because of the use of composite material and, on the other hand, such blades have an increased ductility and protection against erosion because of the metallic first blade section that extends along at least a portion of the leading edge of the blade and the surface area of the blade that borders on the leading edge. In addition, the present rotor blades provide a good vibration attenuation. Because of the metallic blade pan sections, the rotor blades are robust, particularly in the hub area. In the case of breakage, it is a simple matter to repair such composite material blade sections by replacing them. Based on the good damping characteristics with rotors bladed according to the invention, particularly such as compressor rotors or fan rotors, a greater fatigue notching effect resulting from defective areas that appear during operation, for example cracks, can be allowed for the present blades. Consequently, a rotor or its rotor blades according to the invention will require less frequent repair compared to conventional rotors subjected to normal wear.
Preferably, the metallic blade section forms the blade leading edge beginning radially inside at the blade root and ending a distance from the radial outer end of the blade leading edge or the blade surface. In this way, the rotor blades are protected at the flow stagnation point that occurs at the blade leading edge and at the blade surface areas next to both sides of the leading edge around which flow occurs.
Furthermore, it is preferable that the metallic blade pan section has a slot or groove in which the blade of fiber-reinforced synthetic material is held.
It is advantageous that the slot or groove extends completely across an end section, for example, in a curved progression, from a first end that lies on the leading edge of the blade to a second end of the metallic blade pan section that is axially farther back from the first end and is spaced from the blade leading edge.
It can be useful to attach the blade section made of composite material to the metallic blade section by an adhesive bond and/or by rivets.
Furthermore, it is preferable that the blade root and/or the metal blade sections are made of a titanium alloy.
Most preferably, a plurality of fan rotor blades are arranged circumferentially and equidistant from another on a compressor disk and extend essentially radially so as to form an integrally bladed compressor disk, a so-called blisk. In this case, the fan rotor blades are attached to the disk by friction welding or the like to form a single-piece component. This feature reduces the weight of the blisk, which has a positive effect on the damping, as well as the magnitude of the rotational speeds.
Preferably, a circumferentially bladed rotor carrier is a compressor disk, whereby the rotor carrier can alternatively also be a compressor ring.